As a method of dyeing a substance with a non-aqueous dye, a dry dyeing method of precipitating a dye from a gaseous phase to a substance such as vacuum deposition, and a wet dyeing method of precipitating a dye from a liquid phase such as a dye solution and a pigment dispersion to a substance have been used. However, vacuum deposition requires a vacuum apparatus, further, the kinds of dyes that can be proof against a high temperature condition to evaporate dyes are limited in number, so that this method does not necessarily have a wide range of application. On the other hand, the drawback of the liquid phase method is that it is necessary to adopt a measure to reduce environmental load such as the equipments for recovering the vapor of solvent since a volatile organic solvent is used. Even when water is used as the medium, a dispersion process for a long time should be taken to finely disperse a non-aqueous dye in water, further, materials other than a dye such as various surfactants and latex polymers must be added as the auxiliary dispersants, so that this method also does not necessarily have a wide range of application.
On the other hand, a salt called an ionic liquid that is liquid at room temperature was reported by Wilkes et al. in 1992 (e.g., see Chemical Communications, p. 965 (1992)). Ionic liquids are incombustible, nonvolatile, can be used safely and repeatedly, and promising in the field of organic synthesis as an environmentally harmonic reactive solvent (e.g., see Ion-Sei Ekitai—Kaihatsu no Saizensen to Mirai-(Ionic Liquid—The Forefront and the Future of Development-), CMC Publishing Co., Ltd. (February, 2003)). In addition, since an ionic liquid has high ionic conductivity, the use in the field of electrochemistry has spread such that the use as the electrolyte of a secondary battery is discussed, and the use as the electrolyte of a dye sensitization solar battery is proposed (e.g., see JP-A-2001-167808 and JP-A-2002-75470).
However, it was not known to apply an ionic liquid to a coating material and a dyeing method.